The diagram at left shows the system has been fully pressurized. This pressure is equivalent to about a 12,000ft altitude change.
The air inside the sealed chamber has been compressed due to the reduced volume. As a result the refractive index of the air has increased and caused the CWL of the etalon to move to the blue or high energy side of the Hydrogen wavelength.

Due to the fact that there is no tilt involved, the image field remains flat and very precise.

Traditional tilting allows the Doppler shifting across the field in a plane perpendicular to the axis of light. The user can see a change to the image that allows for the viewing of proms and then filaments. The optimum position is when the proms and surface are both fairly detailed. Overtilting will tighten the bandpass but will also produce a banding effect. The resolution under the band is higher, but at the expense of the entire field of view.

People often feel that the entire field should be as good as the area created under the band. If this were possible, the systems would be spec’d at a much lower bandpass. If a band occurs, the system has probably been over attenuated.

True Doppler Tuning allows for a shift into and away from the user. Adding a 3D component to the viewing experience.
While it has minimal effect on proms due to their being at the edge of the disk, it does have an effect on filaments and active regions.
While looking at a filament at the center of the Sun the user has the ability to Doppler shift from the base of the filament to the tip, following the filament thru it’s structure toward you and away from you. Allowing for enhanced visual and imaging capability for the observer as well as a research tool for the avid hobbyist.
The tuning system provides an order of magnitude more precision to the tuning of the desired features.

We are working on designs to the LS100F and the LS100T/Na utilizing the same technology.
The LS100F will be remotely operated for those that have this filter mounted on a long FL scope and do not have 4ft long arms.
We are currently manufacturing the LS60T and the LS100T via this technology.
The LS60T is fully upgradeable to the new Pressure Tune System at any time. However, it does require a return to the factory.

End of Part 3

About Lunt Solar Systems LLC…

Lunt Solar Systems is a manufacturing and sales facility located in Tucson, Arizona. Lunt Solar design, fabricate, assemble, and test solar telescopes and solar filters. Whether you are looking for a dedicated solar telescope or a solar filter for attachment to you own astronomy telescope, we can help. Solar telescopes models start at $499 for an LS35T (telescope) or the LS50F (filter) all the way thru the 152T and the 160F. Solar observing is both fun and educational. Don’t miss out on Solar Maximum. Feel free to contact us with question or comments and we’d be happy to help.

The diagram shown at left indicates that the air pressure inside the sealed chamber has been increased. At this point the CWL of the bandpass is at 656.28nm. At this position we are looking at the Hydrogen-alpha line and the energy associated with that wavelength.

The sealing of the cavity is done via the collimating and refocus lens so that the etalon itself is isolated from differential pressure.
The piston applies from zero to a pressure that is equivalent to taking an etalon from -500ft to +12,000ft above sea level.
This has the added benefit of making the etalon system altitude insensitive.

In addition the etalon can be used from -50 to +200 degrees Celsius due to the fact that the tuning can compensate for the very small changes that heat would have on the “feet” of the etalon.

I have gone into great detail in prior posts regarding the compromises of tilting internal to a telescope. Only very small adjustments to the tilt of an etalon can be done otherwise the etalon system will begin to suffer from the off axis rays of the re-collimated beam.
People have noted that in internal tilt systems the CWL is very sensitive to even small adjustments of the tilt wheel.
By removing the need for tilt we have placed the etalon in the most optimized position possible.
We install a very accurately tuned etalon. This etalon is tuned to the red side of the CWL. Given that it is already tuned to the red, the user has the ability to shift the tune of the CWL to the Hydrogen-alpha line and then Doppler tune to the blue or back thru to the red.

Due to the fact that there is no tilt involved, the image field remains flat and very precise.

Lunt Solar Systems recently introduced the new Pressure Tune system, or Doppler True Tuning system.

The image at left shows the basic outline of this system. The internal etalon is at ambient pressure. The tuning of the etalon is slightly low, putting the Center Wavelength (CWL) at the red wing of the Hydrogen line. This provides a view of less energetic features in the Chromosphere.

How does it work and what does it do?

The system works because the etalons used in the current Lunt designs are air spaced. These air spaced etalons have been typically tuned to the Hydrogen-alpha line via several mechanisms.

The first is the spacing of the air gap between the high reflective surfaces of the ultra flat plates. By changing the spacing, you change the CWL. The distance of this spacing is generally held constant because the refractive index of the medium between the plates (air) is relatively stable at ~1.
The center wavelength can be manipulated from there by slight tilting of the etalon. This changes the angle of the light at the interface of the high reflector/air layer, having the effect of moving the center wavelength toward the blue.

Slight changes in barometric pressure and/or a change in altitude will effect the CWL due to the change in refractive index of the spacer layer.
These changes can be compensated for by additional tilting provided that the etalon is tuned to accomodate those changes.
Taking an etalon that was tuned at 100ft to 10,000ft would certainly not be within that range.

In the past I have manufactured sealed etalon systems for space flight.
These etalon systems were designed to work in a sealed vacuum. As a result they were manufactured as very highly tuned etalons. By placing them under vacuum, the tuning lowered . Tuning was done to ensure that at full vacuum the etalon was on band.
Additional fine tuning from there was done via heat due to the fact that the vacuum could not be adjusted.

Our technology utilizes air pressure and not vacuum.

End of part 1

About Lunt Solar Systems LLC…

Lunt Solar Systems is a manufacturing and sales facility located in Tucson, Arizona. Lunt Solar design, fabricate, assemble, and test solar telescopes and solar filters. Whether you are looking for a dedicated solar telescope or a solar filter for attachment to you own astronomy telescope, we can help. Solar telescopes models start at $499 for an LS35T (telescope) or the LS50F (filter) all the way thru the 152T and the 160F. Solar observing is both fun and educational. Don’t miss out on Solar Maximum. Feel free to contact us with question or comments and we’d be happy to help.